In the past, producers of extruded feed products, such as pet food, fish food, etc., have used combination pan dryer/coolers to dry the extruded food products and cool them in one step. More recently it has become a common practice to first dry the product and then fat and flavor coat it prior to cooling. This is because hot, dry products absorb more fat then cooled products. Thus, separate machines are often used for drying, then fat and flavor coating and then cooling.
A typical prior art cooler which is often used for cooling extruded animal feed is shown and described in U.S. Pat. No. 4,887,364 issued Dec. 19, 1989 to Pierre Geelen, entitled DEVICE FOR COOLING AND/OR DRYING BULK GOODS. In this apparatus, a cooling bunker receives bulk goods to be cooled through a rotary airlock feeder positioned on the top thereof. The bunker has a floor consisting of a number of pivotable bars which form a grate. The bars are designed to allow the passage of cooling air therethrough, which cooling air passes through the bulk material in the bunker and up and out of an exhaust port near the top of the bunker. The bars, when pivoted downward, form a substantially solid floor and, when pivoted upward, allow the passage of bulk material through the floor and into a collection hopper.
A number of problems occur with usage of coolers of the type shown in the Geelen '364 patent for cooling extruded animal feed products. The cooler bunker, and, particularly the grate, tends to collect small chunks of product which hang up on the grid due to the large number of flat surfaces involved. The grids also require a substantial effort to clean between production runs, often causing cross-contamination between product types. Product breakage is also a significant factor since feed pellets are broken when the grids open and close. In addition, a considerable time is spent adjusting the grid settings when production is switched between runs of small products such as fish food (e.g. 1.5 mm diameter range) and large products such as dog food (e.g. 15 mm diameter range). Finally, problems result from smaller pellets tending to leak out of the grid while larger pellets tend to collect on the grid.
It is clear that a need exists for an improved cooler specifically designed for cooling extruded feed products. Such a cooler should efficiently cool the extruded product while minimizing product breakage and allowing reliable and consistent flow through of product regardless of product size. The cooler should also be easy to clean between product runs.